The role of microRNA-23b-5p in regulating brown adipogenesis and thermogenic program.

Enhanced brown adipose tissue (BAT) mass and activity have been demonstrated to promote the expenditure of excess stored energy and reduce prevalence of obesity. Cold is known as a potent stimulator of BAT and activates BAT primarily through the β3-adrenergic-cAMP signaling. Here, we performed RNA-sequencing to identify differential miRNAs in mouse BAT upon cold exposure and a total of 20 miRNAs were validated. With the treatment of CL-316,243 (CL) and forskolin (Fsk) in mouse and human differentiated brown adipocyte cells in vitro, miR-23b-5p, miR-133a-3p, miR-135-5p, miR-491-5p, and miR-150-3p expression decreased and miR-455-5p expression increased. Among these deferentially expressed miRNAs, miR-23b-5p expression was differentially regulated in activated and aging mouse BAT and negatively correlated with Ucp1 expression. Overexpression of miR-23b-5p in the precursor cells from BAT revealed no significant effects on lipid accumulation, but diminished mitochondrial function and decreased expression of BAT specific markers. Though luciferase reporter assays did not confirm the positive association of miR-23b-5p with the 3'UTRs of the predicted target Ern1, miR-23b-5p overexpression may affect brown adipocyte thermogenic capacity mainly through regulating genes expression involving in lipolysis and fatty acid β-oxidation pathways. Our results suggest that miRNAs are involved in cold-mediated BAT thermogenic activation and further acknowledged miR-23b-5p as a negative regulator in controlling thermogenic programs, further providing potential molecular therapeutic targets to increase surplus energy and treat obesity.